Another consistent finding in rats and mice is that restraint stress and chronic unpredictable stress produce a profound and sustained reduction in AEA levels within the amygdala (Patel et al., 2005; Hill et al., 2009). In contrast to 2-AG, reductions in AEA are not related to subsequent stress exposure as 24 hours after the last stress exposure, AEA levels are still profoundly reduced in many brain regions (Hill et al., 2009). In some cases, chronic stress produces an up-regulation of FAAH activity, suggesting increased tonic AEA degradation as a mechanism subserving the sustained reductions in AEA levels after repeated stress (Rademacher et al., 2008; Hill et al., 2009). In contrast to 2-AG, acute corticosterone produces a rapid (within 10 min) elevation of AEA in the amygdala.
